1. Field of the Invention
The present invention relates to a silicone rubber composition for extrusion molding that yields a cured product for which the elastic modulus increases across a temperature range from 30 to 110° C.
2. Description of the Prior Art
Tests are being conducted in which special optical fiber sensors are embedded within high-performance structural materials such as composite materials, and these sensors are then used to continually monitor the structural materials for distortion and the like. For example, a method has been disclosed for measuring the internal distortion within a fiber-reinforced composite material laminate by embedding the sensor portion of an optical fiber interferometer within the layers of a fiber-reinforced composite material laminate, and then using the sensor portion to measure the change in intensity of interference light (see patent reference 1). Furthermore, a method of embedding an optical fiber in an epoxy resin cast article such as an insulating molding for a high-voltage instrument is also known (see patent reference 2). Moreover, a method of embedding an optical fiber as a sensor within a plastic, metal, ceramic, concrete, a composite material that has been reinforced using an inorganic fiber such as SiC or a reinforcing fiber such as stainless steel fiber, or a laminate comprising a single material or a number of different materials, is also known (see patent reference 3).
Known collision sensors include falling rock sensors (see patent reference 4) and vehicle collision sensors (see patent references 5 to 7).
Acrylic optical fibers exhibit superior flexural strength and are more readily processed than silica-based optical fibers or glass-based optical fibers, and are consequently used in a wide variety of fields. However, the elastic modulus of acrylics decreases with increasing temperature, meaning acrylic optical fibers have a large temperature dependency, and are therefore unsuitable for use as optical fiber sensors.
Silicone rubbers exhibit excellent weather resistance and electrical properties, have a low compression set, and exhibit superior properties of heat resistance and cold resistance and the like, and are consequently widely used as matrix materials. By using a liquid silicone rubber for which the elastic modulus increases with increasing temperature, the temperature dependency of an acrylic optical fiber sensor can be significantly reduced, but the workability of such compositions is poor, and they are not suitable for mass production.    [Patent Reference 1] JP 4-361126 A    [Patent Reference 2] JP 11-165324 A    [Patent Reference 3] JP 2001-082918 A    [Patent Reference 4] JP 2002-267549 A    [Patent Reference 5] U.S. Pat. No. 5,335,749    [Patent Reference 6] WO 01/23224 A1    [Patent Reference 7] JP 2006-500284 A